All water on Earth travels through the sun powered, hydrologic cycle. Heat from the sun causes water on the surface to evaporate and rise into the atmosphere where it forms clouds. The water vapor then condenses and falls back to the Earth as rain, snow, or hail. This water will then, either seep into the soil, or it will flow over the Earth’s surface. Either way, all water will eventually reach larger bodies of waters such as rivers, lakes, or oceans, where it will once again repeat the cycle. This flow of water creates kinetic energy and is the first phase of hydropower (U.S Department of Power Resources , 2005). |
In order to transform this kinetic energy into mechanical energy, one of two types of hydropower plants must be used. The first type is called a run-of-the-river plant, which relies on the changes in water flow. It is dependent upon season changes and weather conditions, which control the amount of power by altering how much water flows through the plant (Harnessing Hydropower, 2011). The second type of plant is known as a storage plant or reservoir. This plant is more commonly used as it allows for a steadier water supply.
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For these power plants a dam is built in a river in order to stop the water from flowing downhill, and thereby controlling the power of the water. In order to generate power, the damn opens and water is released through a penstock. The water falls through the turbines to the tail water below. A storage plants energy-producing potential is dependent on both the amount of water in the forebay and the head, which is the height difference between the reservoir and the afterbay (U.S Department of Power Resources , 2005).
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The force of the water flowing through the turbines causes the turbine’s blades to spin. These spinning blades turn the router, which contains an iron frame that has coils of wire wound around it. By being turned the router creates a strong magnetic field which pushes past the generators stationary coil and converts the mechanical energy into electrical energy. From here the energy is carried through transmission lines to a switchyard. Here, the voltages are increased in order to transmit it long distances across the country. The electricity will then be sent to substations where local utilities will distribute it to homes and businesses in the area but first the voltage will be reduced so that it is safe for use (Harnessing Hydropower, 2011).